I'm not entirely sure it is now just on the low E string as I was trying to play the intro to sweet child
o mine last night and it got a buzz on the 12th fret of the D string.
Yes the guitar is used and the guy I bought it off said he had had the guitar for about 12 months and recently put new strings in it.
What I think may be the best option is during the christmas break take the old strings off and examining the fretboard and also cleaning it. Then re-string it with a new set of strings (so I then know exactly what it has) & then look at adjusting the action from there.
As I have only been playing guitar 3 weeks I think this may well be good practise for general guitar maintenance.
I have read that FastFret is a good for the fretboard. Can anyone else recommend anything else to try/use??